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lou's garage

I just had spark plugs and ignition coils put in my 2005 Ford 500. Now I hear a knocking noise. What could be causing the noise? – Lynda

The easiest answer is that perhaps a spark plug has been installed that is not correct to your vehicle, or one of the new spark plugs or coils is defective.

If everything with the previous repair checks out, you will need to identify the noise as either being a preignition knock or a knock associated with a mechanical engine failure.

Considering that you just had ignition coils replaced, I suspect that your engine had a misfire and that the malfunction indicator light (MIL) illuminated, sending you in for service.

If you drove for an extensive period with the MIL illuminated and the engine misfiring, the powertrain control module (PCM) will have made dramatic changes to its fuel trim parameters.

Now that the ignition system is working correctly, the PCM will slowly return to its original settings and the knock or ping may be a temporary byproduct and will correct itself.

However, driving a vehicle that is misfiring may also have catastrophic results as every time the engine misfires, raw non-burned fuel will be sent down the tail pipe and also in to the engine oil pan.

The engine oil will become contaminated with gasoline and fail to do its job as a lubricant. Head back in to your service provider. It might be nothing, but you need to deal with this now if it’s not.

Many cars are now being equipped with turbochargers. How do you check for damage when purchasing an equipped used vehicle? I am especially concerned because a turbo works at very high RPMs, derives its power from the extremely hot and corrosive environment of exhaust gases, and can be easily damaged if the engine is switched off without a cool-down idle, or oil and filter changes are delayed. – Bill C.

You are quite right; turbocharged vehicles are now common in the marketplace.

The very first thing you can do as a prospective buyer is to research reliability reports for the vehicle in question. Sourcing the vehicle’s service history, paying particular attention to correct oil-change intervals is also imperative.

Additionally, a failing turbocharger will likely cause the engine to consume oil, so be sure to check the oil level and look for smoke from the exhaust. Have a technician perform a prepurchase inspection with road test looking for a lack-of-power condition associated with a boost issue.

Be sure to have them check the body of the turbocharger for any oil or coolant leaks. If you’re lucky, access may be generous, and a technician may be able to remove turbo inlet house and use a borescope camera to peer inside, or use their finger to feel the turbocharger shaft and determine if has excessive play.

Any used car you might be considering with a malfunction engine light illuminated needs to be vetted for turbo-related trouble codes.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail, placing “Lou’s Garage” in the subject line.

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